1. Field of the Invention
The present invention relates to a device and a method utilized in semiconductor fabrication, and more specifically, to a device and a method for testing an exposure apparatus.
2. Description of the Prior Art
The photolithography process is the most important step in semiconductor fabrication and the process transfers the layout of a designed integrated circuit onto a semiconductor wafer. Typically, to implement the photolithography process, a designed pattern such as a circuit layout pattern or an ion doping layout pattern in accordance with a predetermined design rule is created on one or several mask in advance, and the pattern on the mask is then transferred by light exposure onto a photoresist layer on the wafer.
Additionally, a step-and-scan exposure apparatus is usually applied in the photolithography process. The step-and-scan exposure apparatus includes a light source for generating light beams, a mask stage utilized for holding a mask having a predetermined pattern and moving the mask, a wafer stage utilized for holding a semiconductor wafer and moving the semiconductor wafer, and a surface topography detection system or a height/tilt detection system utilized for measuring a surface topography of the semiconductor wafer.
Before an exposure process is performed on the semiconductor wafer that is put on the wafer stage, the step-and-scan exposure apparatus utilizes the surface topography detection system to measure the surface topography of the semiconductor wafer, thereby obtaining the surface information, which records the surface topography of the semiconductor wafer. Then, the step-and-scan exposure apparatus utilizes the wafer stage to adjust a height or a tilt angle of the semiconductor wafer according to the surface information measured by the surface topography detection system, so that a surface of the semiconductor wafer can be located on a focal plane of the exposure apparatus. Thereafter, light beams such as i-line, KrF laser or ArF laser are generated by the light source of the exposure apparatus, and then, the light beams passing through the mask and projection lenses are projected onto a photoresist layer on the semiconductor wafer for transferring the predetermined pattern of the mask onto a region (or a shot) of the semiconductor wafer. Subsequently, the wafer stage and the mask stage are moved towards different directions for performing the above-mentioned exposure step repeatedly, and therefore, the predetermined pattern of the mask can be transferred onto the entire semiconductor wafer.
As mentioned above, the surface of the semiconductor wafer should be precisely located on the focal plane of the exposure apparatus so that the predetermined pattern of the mask can be accurately transferred onto the entire semiconductor wafer. Accordingly, the calculation function of the surface topography detection system as well as the drive function of the wafer stage should work quite accurately so that the surface of the semiconductor wafer can be precisely located on the focal plane. However, since there are various kinds of step-and-scan exposure apparatuses, it is very hard for process engineers or equipment engineers to immediately verify both the calculation function and the drive function of each exposure apparatus when they survey exposure apparatuses. As a result, it is an important and urgent issue to establish a device and a method for verifying both the calculation function and the drive function of an exposure apparatus.